One of the last steps of manufacturing a good prior to packaging is coating; most commonly referred to as painting. In addition to the aesthetic value, coating protects the good from the elements that cause corrosion. As would be known in the industry, manufactured goods require surface preparation before they are subjected to a final coating stage, such as a painting stage. Surface preparation typically involves degreasing or cleaning and subsequent coating pretreatment steps. Finished goods (e.g., auto parts, appliance parts, furniture parts, heavy equipment) are commonly fabricated from sheet, roll, forged, cast, and/or extruded materials (e.g., steel, aluminum, zinc, zinc coated, copper, plastic). During fabrication, process fluids (e.g., buffing compounds, coolants, greases, lubricating oils, rust inhibitors, pressworking fluids, and quench oils) are necessary to enable efficient and quality production. Cleaning is required to remove these process fluids, material fines/shavings, and other surface debris or contaminants that are generated as a result of the manufacturing process. Subsequent pretreatment steps are required to ensure coating adhesion and corrosion resistance. Corrosion remains a significant concern when processing metal parts. In addition to degrading the aesthetic look and feel of the metal parts, it also can degrade the mechanical properties and the strength of the metal parts. Consequently, pretreatment of metal substrates has been utilized to produce anti-corrosive properties and longevity of the metal substrate.
Conventional methods have utilized various pretreatment methodologies to address corrosion. Pretreatment with metal phosphate primers (e.g., zinc or iron phosphate) have been used; however, metal phosphates are environmentally undesirable. Furthermore, after pretreatment with metal phosphate primer, the next steps may include a rinse using chromic acid prior to painting the metal surface. Chromium based systems, while providing strong anti-corrosive properties, also are not environmentally desirable and present worker safety issues.
Accordingly, there is a need for pretreatment coatings which are environmentally friendly, while providing anti-corrosion benefits and enhanced paint adhesion.